Over the past few years, cameras have been remarkably electronized, and many operations which had previously depended on the experience and perception of human operators are now automatically performed by electronic control, for example, the control of exposure and the automatic control of a camera-to-subject distance. Microcomputers are often used as circuits for electronic control in view of the degree of freedom of control and reductions in development period.
Although a battery is generally used as a power source of a camera, the voltage of the battery in a camera that has a strobe unit or an auto-loading function for automatically rolling up films can temporarily vary. In such a camera, the source voltage of a microcomputer would also vary, resulting in malfunctioning of the microcomputer. It is therefore necessary to use a step-up power source as a source voltage of such a microcomputer.
However, there is a danger that, if the voltage of the step-up power source is not sufficiently high when the microcomputer starts up even after it has been stepped up, or if the voltage of the step-up power source is not completely stepped up and drops for some reason during the operation of the microcomputer, the operation of the microcomputer becomes unstable, resulting in malfunctioning.